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Can cyclodextrins really improve the selectivity of extraction of BTEX compounds?

  • Klára Balogh
  • Nikolett Szaniszló
  • Klára H-Otta
  • Éva Fenyvesi
Original Article

Abstract

Solubility of BTEX compounds was determined in aqueous solutions of natural CDs (α-, β-, γCD) as well as of some industrial βCD derivatives (RAMEB, HPBCD, AcβCD) measured by UV photometry. From the phase solubility diagrams the complex association constants were determined. The βCD derivatives increased the solubility of individual monoaromatic compounds, depending on the structure of the guest molecule. We have found that RAMEB (randomly methylated βCD) and AcβCD (partially acetylated βCD) are the most effective solubilizers while the effect of natural CDs is not significant because the complexes precipitate from the solutions. Extraction experiments were performed to see how the complexation of components influences the extraction using a mixture modeling the composition of these pollutants in soil. We have found that although the soluble CD derivatives are not as selective as expected based on complex association constants, they increased the efficacy of extraction by 4–6 times. The reason of the low selectivity is that the concentration ratio of certain BTEX compounds in CD solutions is smaller than in water. CD derivatives seem to have an equalizing effect: the solubility of the least soluble p-xylene is improved in the highest extent, but that of benzene the least. This result, however, is an advantage in the application of these CD derivatives in soil remediation (the availability of each BTEX compounds will be enhanced).

Keywords

Benzene Xylene Complex association constant Solubility Cyclodextrin derivatives Soil remediation 

List of abbreviations

BTEX

Mixtures of benzene, toluene, ethyl benzene and xylenes

AcBCD

Acetyl β-cylodextrin

CD

Cyclodextrin

HPBCD

Hydroxypropyl β-cyclodextrin

HPLC

High Performance Liquid Chromatography

K

Complex association constant

RAMEB

Randomly methylated β-cyclodextrin

Notes

Acknowledgements

The work was supported by Hungarian Research Fund (NKFP3/002/2001 and NKFP3/020/2005) and Economic Competitiveness Operative Programme (GVOP-3.1.1.-2004-05-0257/3.0), which is greatly acknowledged.

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Copyright information

© Springer Science+Business Media, Inc. 2007

Authors and Affiliations

  • Klára Balogh
    • 1
    • 2
  • Nikolett Szaniszló
    • 1
  • Klára H-Otta
    • 2
  • Éva Fenyvesi
    • 1
  1. 1.Cyclolab Cyclodextrin R&D Laboratory Ltd.BudapestHungary
  2. 2.Department of Chemical Technology and Environmental ChemistryBudapestHungary

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